Clinical assessment of muscle condition in cats

In cats, loss of muscle mass may result from ageing (sarcopenia) or from multiple chronic conditions, including chronic kidney disease, hyperthyroidism, congestive heart failure, and cancer (Baez et al, 2007; Freeman, 2012; Santarossa et al, 2017; Santiago et al, 2020). In some cases, subtle atrophy of skeletal muscle may be one of the only physical examination manifestations of the early stages of these diseases. In addition, progressive loss of muscle mass secondary to disease, termed cachexia, may be associated with a worse prognosis (Finn et al, 2010; Freeman, 2012; Miyamoto et al, 2016; Santarossa et al, 2017; Santiago et al, 2020). However, muscle wasting in cats can be easily missed if muscle condition is not specifically evaluated. Chronic disease, and subsequent chronic inflammation, create states within the body in which muscle breakdown occurs, while fat mass may increase or remain stable (Freeman, 2012; Santarossa et al, 2017). As such, weight and overall body condition may be unchanged or even increasing, while ongoing loss of muscle tissue is occurring secondary to disease. While sarcopenic muscle loss occurs with age in the absence of disease, assuming that cats with muscle wasting are ‘just getting old’ risks missing the diagnosis of manageable chronic diseases and losing the chance to increase both quantity and quality of life for feline patients.